The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2000-175186 filed Jun. 12, 2000
1. Field of the Invention
The present invention relates to an eye cup moving mechanism of an optical device having an eye cup, such as a telescope, a binocular or a microscope.
2. Description of the Related Art
The eye cup of an optical device, which is mounted at the eyepiece unit, is moved along the direction of the optical axis of the eyepiece lens to offer a comfortable visual field to both a user wearing glasses and a user who does not wear glasses. An eye cup in the prior art is rotated around the optical axis of the eyepiece lens to travel along the direction of the optical axis, and its traveling distance is regulated by a cam mechanism.
FIG. 5 is a longitudinal sectional view of the structure adopted in an eye cup moving mechanism in the prior art. An eye cup 20 is constituted by securing an eye cup cover 11 around the external circumference of an eyepiece outer casing 12. The eyepiece outer casing 12 is formed in a cylindrical shape, and its internal circumferential surface is allowed to slide against the external circumferential surface of an eyepiece lens holding barrel 14. The external circumferential surface xe2x80x9csxe2x80x9d of the eyepiece lens holding barrel 14 is formed to extend straight along the direction of the optical axis. With the eyepiece outer casing 12 moving relative to the eyepiece lens holding barrel 14 along the external circumferential surface xe2x80x9csxe2x80x9d, the distance between an eye cup front end 20a and the outer end surface of the eyepiece lens is varied.
In FIG. 5, the eye cup front end 20a is at position d1 which sets the eye cup in an driven-out state. When the eye cup front end 20a is at position d2 indicated by the dotted line in the figure, the eye cup is in a driven-in state. The eye cup front end is set at position d1 or d2 by employing a cam mechanism constituted of camshafts 15a and 15b provided at the eyepiece lens holding barrel 14 and a cam groove (not shown) formed at the eyepiece outer casing 12. It is to be noted that the eyepiece lens holding barrel 14 normally holds a plurality of eyepiece lenses and is mounted at the optical device main unit on the objective lens side.
FIG. 6A is a top view, FIG. 6B is a side elevation, FIG. 6C is a bottom view and FIG. 6D is a side elevation of the half cylinder obtained by slicing the top view in FIG. 6A through line Xxe2x80x94X, all provided to illustrate the structure of the eyepiece outer casing 12 in the prior art.
Simply put, the eyepiece outer casing 12 is a cylinder having two cam grooves 16a and 16b set at 180xc2x0 relative to each other at the cylinder surface. The camshafts 15a and 15b in FIG. 5 engage with the two cam grooves 16a and 16b respectively. When the camshafts 15a and 15b are each at position d1, the eye cup 20 is set in a driven-out state, whereas when the camshafts 15a and 15b are at position d2, the eye cup 20 is set in a driven-in state. When the eye cup 20 is retained at either position d1 or d2, the camshafts 15a and 15b are each pressed at an end of the cam groove 16a or 16b. In other words, the movement of the eye cup is regulated by the cam mechanism.
When the camshafts are retained to set the position of the eye cup, the camshafts are pressed against the cam grooves, and thus, the greatest force is applied where the camshafts are mounted at the eyepiece holding barrel. In an optical device having a compact eyepiece unit, in particular, small camshafts that are mounted (e.g., screwed in) over a small screwing diameter are naturally used.
The eye cup cover for the eye cup is often constituted of rubber, and when it is rotated, a large moment is generated to result in an impact force manifesting upon the camshafts becoming pressed against the ends (position d1 or d2) of the cam grooves. In a worst case, the areas over which camshafts are mounted that are most greatly affected by the impact force may become damaged. The ends of the cam grooves, too, are subject to the impact force.
An object of the present invention is to provide an eye cup moving mechanism that prevents camshafts and cam grooves from becoming damaged even when a great force is applied.
In order to attain the above object, an eye cup moving mechanism of an optical device according to the present invention, comprises: an eyepiece lens holding barrel that houses and holds an eyepiece lens; an eyepiece outer casing that is capable of sliding against an external circumferential portion of the eyepiece lens holding barrel; and an eye cup cover provided at the eyepiece outer casing. The eyepiece lens holding barrel includes a first regulating member provided at the external circumferential portion thereof; and the eyepiece outer casing includes a second regulating member that comes in contact with the first regulating member to regulate a movement of the eye cup cover along an optical axis of the eyepiece lens.
In this eye cup moving mechanism of an optical device, it is preferred that the eyepiece lens holding barrel and the eyepiece outer casing are relatively moved along an optical axis of the eyepiece lens by a cam mechanism constituted of a cam shaft provided at either the eyepiece lens holding barrel or the eyepiece outer casing and a cam groove formed at either the eyepiece lens holding barrel or the eyepiece outer casing at which the camshaft is not provided; and the first regulating member at the eyepiece lens holding barrel and the second regulating member at the eyepiece outer casing are provided so as to come into contact with each other before an end of the cam groove comes in contact with the camshaft.
Also, it is preferred that the first regulating member comprises a third regulating member and a fourth regulating member; the second regulating member comprises a fifth regulating member and a sixth regulating member; the third regulating member at the eyepiece lens holding barrel and the fifth regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven-out furthest toward a user; and the fourth regulating member at the eyepiece lens holding barrel and the sixth regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven in furthest from the user. In this case, it is preferred that the third regulating member and fourth regulating member are formed so as to project outward at the external circumferential portion of the eyepiece lens holding barrel; the fifth regulating member is formed so as to project inward at an internal circumferential portion of the eyepiece outer casing; and the sixth regulating member is constituted of an end of the eyepiece outer casing located on a side opposite from the user. Furthermore, it is preferred that a cutting portion is provided at a portion of at least either the third regulating member or the fifth regulating member so as to ensure that the third regulating member and the fifth regulating member do not come in contact with each other.
Also, it is preferred that the first regulating member at the eyepiece lens holding barrel and the second regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven-out furthest toward a user. In this case, it is preferred that the first regulating member is formed so as to project outward at the external circumferential portion of the eyepiece lens holding barrel; and the second regulating member is formed so as to project inward at an internal circumferential portion of the eyepiece outer casing. Furthermore, it is preferred that a cutting portion is provided at a portion of at least either the first regulating member or the second regulating member so as to ensure that the first regulating member and the second regulating member do not come in contact with each other.
Also, it is preferred that the first regulating member at the eyepiece lens holding barrel and the second regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven in furthest from a user. In this case, it is preferred that the first regulating member is formed so as to project outward at the external circumferential portion of the eyepiece lens holding barrel; and the second regulating member is constituted of an end of the eyepiece outer casing located on a side opposite from the user.
A telescope according to the present invention comprises at least one eye cup moving mechanism. The eye cup moving mechanism comprises: an eyepiece lens holding barrel that houses and holds an eyepiece lens; an eyepiece outer casing that is capable of sliding against an external circumferential portion of the eyepiece lens holding barrel; and an eye cup cover provided at the eyepiece outer casing. The eyepiece lens holding barrel includes a first regulating member provided at the external circumferential portion thereof; and the eyepiece outer casing includes a second regulating member that comes in contact with the first regulating member to regulate a movement of the eye cup cover along an optical axis of the eyepiece lens.